Process of making cellulose acetate



Patented July 6, 1926. I 1 I UNITED STATES PATENT OFFICE...

WILLIAM R. WEBB AND CARL J. MALM, OF ROCHESTER, NEW YORK, ASSIGNORS T EASTMAN KODAK COMPANY, OF ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK.

PROCESS OF MAKING CELLUI TOSE ACETATE.

NoDrawing. Application filed October 7,1925. Serial No. 61,144.

This invention relates to processes of chloride is employed as the catalyst. Evimaking cellulose acetate. One object of the dently when the phosphorus and chlorine 65 inventlon is to provide a safe, rapid and act on each other in the acetylating bath,

. easily controlled process which will yield they produce an active compound in a nascellulose acetate free from serious degradacent or especially reactive condition;

tion. Another object of the invention is We shall now describe the preferred form to provide a process in which the costs of our invention by way of example, but 60 caused by the material being tied up in it will be understood that the invention is the plant for a prolonged time are greatly not limited to the details, thus given, except lessened. Other objects will hereinafter apas indicated in the appended claims. An

ear. acetylating bath is prepared by mixing 500 We have found that cellulosic material parts of glacial acetic acid and 600 parts of 65 may be rapidly and safely acetylated, withacetic anhydride. This is mixed with 100 out serious degradation, by treating it with parts of the cellulosic material, which may 1 an acetylating bath, the action of which is be any of the materials customarily used in catalyzed by means of phos horns and chlothe manufacture of cellulose acetate, such as rine. Preferably the acetylating bath concotton, tissue paper, wood pulp etc. We 7 tains glacial acetic acid and acetic anhyhave found that 100 parts of clean cotton dride. Either the yellow or red forms of are especially useful in producing a highphosphorus may be employed. But because grade product. Into the mixture of cotton of the intensity with which chlorine acts and the acetylating bath there is stirred with yellow phosphorus, because of the from 1 to 10 (say 4 parts) of red phos- 5 danger of degrading the product by. the phorus. This should be distributed with consequent rapid evolution of heat when yeluniformity throughout the reaction mass.

low phosphorus is used, because of the haz The latter is preferably kept at a temperaard to the employees when yellow phosphorture sufliciently low to prevent the degraus is used, and because of the expenses of dation of the cellulose acetate which is 80 refrigeration which is desirable to control being produced. We have found to the action of the yellow phosphorus, we 0. to be a safe working temperature by way greatl prefer to employ red phosphorus. of illustration.

This oes not produce a harmful evolution With the reaction mixture, containing the p of heat, when acting with the chlorine, but red phosphorus, at the proper temperature,

the operation is under adequate control and We ass in gaseous chlorine b bubbling it yet induces acetylation of the cellulosic maup t rough the mass, preferab y with agitas5 terials at a surprisingly rapid rate. tion of the latter. The chlorine may be We have found that the introduction of forced in so as to itself cause this agitation,

" the phosphorus and chlorine into the acetyorthe action of the chlorine may be sup- 'lating mixture before they have combined pleme'nted by a meehanical'stirring mechawith each other induces a much stronger nism. Chlorine is pa$ed in until it ceases to 4 catalytic action than do chlorinated combe absorbed,-that is, until the bath is satupounds of phosphorus under parallel condirated with 1t, as indicated by the evolution tions. Some of the compounds of (phosphoror increased evolution of chlorine bubbles at us and chlorine have been form to have the upper surface. practically no catalyzing action with respect The cotton gradually goes into solution, as

- to the acetylating of the cellulose and cause the cellulose acetate is formed, and eventualthe production of abadly degraded matcly a clear solut'on will be obtained. .When rial,that is, one in which the cellulosic operating at th temperatures and with the 10 molecule is badlytbroken down. We have proportions given above, the acetylation of found in some examples that red phosphorus cotton linters, in atypical example, has been 50 and chlorine, when introduced uncombined found to be completed within the comparainto the acetylating mixture bring about tively short time of five or six hours. Beacetylation in one-fourth to one-sixth of cause of the rapidity of the reaction, under the time required when phosphorus pentathe influence of our catalysts, we. largely avoid the degradation of the cellulose acetate. product Which takes place when slower acting baths subject the materials to deleterious agents for longer periods.

In the example given above, the cotton is added to the bath before the chlorine. We have found, however, that the process works very well when the chlorine is added before the cotton,that is, when the red phosphorus, preferably in finely divided fOlllt. is stirred into the acetylating bath so,

as to be suspended homogeneously therein and then chlorine bubbled into the bath until the latter is saturated. \Vhen cotton is added to this bath, loaded with the catalyzers, it acctvlatcs very quickly.

After the transparent solution of cellulose acetate is obtained, the subsequent treatment of the materials follows the known practice. The cellulose acetate may be hydrolized to the desired extent, for the production of solubility in specific desired organic solvents. The acetic values may be recovered by evaporation and condensation, or by solution and concentration. llloreover, in the recovery treatment the cellulose acetate may be spread in the form of films or brought into the form of: powder by stirring or spraying, as set forth in the prior art. It is one ot the results of our process that the product is highly tree "from objectionable color.

Having thus described our invent ion, what We claim as new and desire to secure by Letters Patent-is 1. The process of making cellulose acetate Which comprises treatin cellulosie material with an acetylating ath and catalyzing the reaction with phosphorus and chlorine.

2. The process of making cellulose acetate which comprises treating" cellulosie material with acetic anhydride and acetic acid in the presence of red phosphorus and chlorine as oatalyzers.

3. The process of making cellulose acetate which con'iprises distributing red phosphorus homogeneously through an acetylating bath containing acetic anhydride and acetic acid, and treating cellulosic material in said bath in the presence of chlorine until cellulose acetate is produced.

41-. The process of makingcellulose acetate which comprises mixing cotton with acetic acid and acetic anhydride, distributing red phosphorus, equal to l to 10% of the weight of the cellulose, homogenouslythroughout said mixture, saturating the mixture with chlorine. and conducting the reaction at (it) to (35 C.

Signed at Rochester, New York, this 30th day of September, 1925.

WILLIAM R. WEBB. cant a. Mama.

tltl 

